It is difficult to provide monitoring recommendations for lymphoma in kidney transplant recipients without knowing how soon after transplantation this condition occurs.OBJECTIVE
To characterize the timing of (and the demographic risk factors for) lymphoma after kidney transplantation.DESIGN AND INTERVENTION
Patients with end-stage renal disease whose main insurance provider was Medicare, who had no history of renal transplantation, and who joined the US transplant waiting list between January 1990 and December 1999, were identified from the 2001 US Renal Data System database. The incidence of lymphoma in patients who underwent transplantation, from the time of joining the waiting list until death, censoring at 3 years after transplantation, loss to follow-up, or study end in December 1999, was compared with the incidence among patients receiving dialysis who were on the transplant waiting list. The influence on risk of lymphoma of variables including age, race, gender and post-transplantation interval was assessed using Cox proportional hazard regression analysis.OUTCOME MEASURE
The primary outcome was lymphoma.RESULTS
Among the 49,215 patients who received a transplant and were eligible for analysis, there were 357 cases of lymphoma. The incidence of lymphoma was higher in patients who had undergone transplantation than in the 40,045 dialysis patients awaiting transplantation (33.27 cases per 10,000 person-years vs 15.53 cases per 10,000 person-years). Whites (n = 35,212) had a higher incidence of post-transplantation lymphoma than African Americans (n = 14,003; 37.75 cases per 10,000 person-years vs 21.56 cases per 10,000 person-years). In the first year after transplantation, lymphoma occurred most frequently in patients aged <25 years (64.5 cases per 10,000 person-years), but in the first year after placement on the waiting list, lymphoma rates were highest in patients aged >60 years (31.7 cases per 10,000 person-years). The relative risk (RR) of lymphoma remained higher for patients who had received transplants than for those awaiting transplantation when age, gender, race and duration of dialysis before joining the waiting list were taken into account (RR 1.98; 95% CI 1.63-2.40). African American race was associated with a reduction in the adjusted RR of lymphoma (RR 0.58; 95% CI 0.44-0.76). Hazard regression analysis, adjusting for gender and duration of dialysis, showed that the RR of lymphoma in whites who received a transplant compared with whites on the waiting list declined progressively during successive 6-month intervals after transplantation. The highest rates of lymphoma occurred in patients aged <25 years (RR 13.82 for the first 6 months after transplantation; 95% CI 3.96-48.15; P<0.001); after 12 months, only patients in this group remained at significantly higher risk of lymphoma relative to dialysis patients (RR 7.49 at 12-18 months; 95% CI 1.92-29.18; P = 0.004). The pattern of lymphoma risk over time was comparable in African Americans to that in whites. Gender did not significantly alter the adjusted RR of post-transplantation lymphoma in either whites or African Americans.CONCLUSION
Among kidney transplant recipients, the risk of lymphoma varies with age, race, and time since transplantation.